An acoustic generator such as a piezoelectric speaker has conventionally been known as a small and low-current driven sound device in which a piezoelectric substance is used as an electroacoustic transducer, and is used as an acoustic generating device incorporated into a small electronic device such as a mobile computing device.
In general, an acoustic generator in which a piezoelectric substance is used for an electroacoustic transducer has such a structure in which a piezoelectric element serving as an exciter formed with electrodes made of, e.g., thin silver film is pasted to a metal diaphragm. A sound generation mechanism of the acoustic generator in which the piezoelectric substance is used for the electroacoustic transducer generates distortion in the form of the piezoelectric element by applying an alternate current voltage to both surfaces of the piezoelectric element, and transmits the distortion in the form of the piezoelectric element to the metal diaphragm, thereby generating sound.
An acoustic generator using a resin film as a diaphragm instead of a metal diaphragm is also known. In this acoustic generator, a bimorph multilayer piezoelectric element is sandwiched by a pair of resin films in the thickness direction, and further, this resin film is fixed to a frame member with a tension. Accordingly, this improves the sound conversion efficiency, and enables generation of a high level sound pressure.